NUTRITION 



3 6 9 



sunlight, i.e. a narrow bar of light dispersed into a band of different 

 wave lengths, each group of waves produces its appropriate effect and 

 we see a band of blending colors, dark red at one end, running through 

 red, orange, yellow, green, blue, indigo, violet, and ending in the dark- 

 est violet. On interposing a leaf in the path of the light, there appear 

 across the spectrum dark strips due to the partial or complete stoppage 

 of the energy. Similar absorption bands, slightly -displaced, are seen by 

 using in the same way an alcoholic solution of chlorophyll (fig. 648). 



EA 



FIG. 648. Absorption spectra: A, chlorophyll of Allium ursinum in alcohol; B, 

 chlorophyll of English ivy (Hedera Helix) in alcohol; C, chlorophyll of Oscillator ia in 

 alcohol; D, carotin, i, 2, 3, 4, absorption bands of chlorophyllin; 7, //, ///, absorp- 

 tion bands of carotin; EA, end absorption. The lettered broken lines mark the position 

 of the principal absorption lines of the solar spectrum (Fraunhofer lines); the numbered 

 solid Jines form a scale from which wave lengths (X) in millionths of a millimeter may be 

 found by adding a cipher; note the increasing dispersion from left (red) to right (violet). 

 After KOHL. 



These absorption bands are as follows: i, in the red a wide black one, its wave 

 lengths (X) being 670-635 /A/* 1 ; 2, a narrower and less intense one in the orange, 

 X = 622~597 /A/A; 3, in the yellow, a band much lighter than 2, and shading 

 out on the sides, X = 587-565 /A/A; 4, a faint band in the green, not always 

 to be seen, and probably due to decomposition products, X= 544-530 /t/*. Or- 

 dinarily the other three blend into one, and there are no visible waves left beyond 

 the blue (X = 495-420). By very careful manipulation, using dilute solutions in- 

 stead of a leaf, they can be distinguished, their limits not being sharply marked. 

 1 The exact location of the bands varies. i /A/A = o.oooooi mm. 



C. B. & C. BOTANY 24 



